If you play at paintball fields keep in mind that some fields will stipulate full face protection (while others may say goggles only in which case the goggles+neoprene mask will work). As well usually it will have to follow ASTM standards and be ASTM certified.

Other than that, if you play at a private field or dedicated airsoft field the face mask will work to a degree. It's much better however to have a shemagh over your head since the "folds" will absorb the impact and slow down the projectile (due to the "crushing" effect of the folds in the headwrap and momentum transfer/dissipation kind of like the idea behind why speedballers wear the baggiest clothing ever so that paintballs lose velocity and their jerseys "catch" the paintball and it doesn't explode and mark them out).

Other than that the only other suggestion I can come up with is a mesh face mask. Make sure it's "stamped" mesh and not "woven" mesh, on Arnies there was a thread about the quality/design specs of each style of making the mesh and although at the velocities we play at it won't really break the mesh it's still better to have a safety (or "comfort") item overdesigned than designed within specifications but with no overhead. IIRC the woven mesh will be worn down and break after repeated 550-600 FPS strikes while the "stamped" mesh can take much higher velocities. I'll try to dig up the thread.